The two New Zealand motorsport enthusiasts who created Hampton Downs are seeking national and international investment to secure the long term future of the circuit.

Tony Roberts and Chris Watson have launched a campaign to explore interest in either purchasing or further funding New Zealand's newest motorsport facility, a 350-acre complex, located 60km south of central Auckland.

"In order to develop Hampton Downs, and take it to the next level; additional funding is required and this investment needs to come from an outside source," Tony Roberts, the managing director of Hampton Downs, said.

"Chris Watson and I have taken the dream about as far as we can on our limited resources. We have therefore engaged the Bayleys agency to present and market Hampton Downs to new investors.

"The next logical step is the development of the 1.2km track extension, which would then give us three track options ... the current 2.7km circuit, the 1.2km club circuit and the full international 3.8km circuit."

Roberts said the partnership that conceived and created the $70m investment into the International motorsport complex wants to see the 1.2km track extension, corporate suites and race control tower completed as part of the vision.

"We want to complete full 3.8 km circuit that Chris and I dreamed of creating when this project first began in 2004," Roberts said.

"The basic layout for the extension was done at the same time as the construction of our existing 2.7 km circuit. The foundations were compacted and preloaded five years ago so we already have good foundations for the final sealing."

Last year Hampton Downs was controversially overlooked as the venue for the New Zealand round of the Aussie V8 Supercars. Millions of dollars, including public money, is being poured into sprucing up the old Pukekohe complex which won the rights to take over from Hamilton.

Hampton Downs will this weekend host the opening round of the New Zealand V8 Supertourers.